If you set out to build a flying robot, you might think Rule #1 would be: don't crash into stuff. That's because tiny flying machines have a tendency to break when they slam into things. But researchers at the Laboratory of Intelligent Systems removed that rule, instead building an "insect-like, crash-happy robot" called GimBall.
GimBall takes a lesson from insects; if you've ever seen a fly trying to navigate, you'll see that it repeatedly crashes into windows and other objects, but those impacts don't deter it. GimBall has a frame to protect it, and happily crashes into objects while trying to achieve a general goal, such as "go north." Here's a two-minute video showing how it works:
I, for one, welcome our new insectoid robot overlords.
If you're into this kind of thing, I urge you to seek out the documentary Fast, Cheap, & Out of Control (Amazon / Netflix DVD / YouTube) by Errol Morris. It has major segments featuring Rodney Brooks examining this kind of problem with walking robots. In the film, Brooks discusses how insects like ants fall down constantly while walking, but that doesn't make them unsuccessful walkers. That realization led to some of Brooks's most interesting robots.